Fig. 2. opa is spatially restricted in both peripodial epithelium and cells of the disc proper in eye/antennal discs. The expression of opa was examined by RNA in situ hybridization and immunohistochemistry, and analyzed by confocal microscopy. The antennal disc is up in both A and B. (A) opa RNA expression by fluorescent in situ hybridization, 2D projection of confocal optical sections through the eye/antennal disc. The bracket indicates non-imaginal disc cells (adepithelial cells or hemocytes) in the preparation that also hybridize with opa probe. The arrow indicates medial disc proper antennal ring; the arrowhead indicates lateral peripodial epithelium staining. The lateral side of the ring in the disc proper is obscured by the broad peripodial expression in this photo. (B) ß-galactosidase expression is directed by the opa enhancer trap opa^3D246. The white line shows the area of z-section, and corresponds to the xz-image shown in (C). The arrows indicate the antennal ring in the disc proper. The arrowheads in B and C indicate peripodial epithelial staining. (D) Fate map of third instar disc. ANT, antennal disc; EYE, eye disc. (E) Schematic diagram of head structures. Shaded areas indicate position of primordia on adult head. ANT, antennae; AR, aristae; PAL, maxillary palps; VI, vibrissae.